can you think of five famous people who you feel are rational/logical?
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Can you think of five famous people who you feel are rational/logical?. Deciding whether a syllogism is valid. Trying to decide if a syllogism is valid is not easy. Venn diagrams can help (at last a good use for Venn diagrams!). Deciding whether a syllogism is valid. Mmmmmmm…Vodka!. - PowerPoint PPT PresentationTRANSCRIPT
Deciding whether a syllogism is valid
Trying to decide if a syllogism is valid is not easy.
Venn diagrams can help (at last a good use for Venn diagrams!)
Deciding whether a syllogism is valid
• Some IB students are from Russia
• All Russians are good at drinking vodka
• Therefore some IB students are good at drinking vodka
Is this a valid argument?
Mmmmmmm…Vodka!
Using Venn diagrams
• Some IB students are from Russia
IB Students
Russians
IB Students who are Russian
Using Venn diagrams
• All Russians are good at drinking vodka
IB Students
Russians
Good vodka drinkers
Using Venn diagrams
• Therefore some IB students are good at drinking vodka
IB Students
Russians
Good vodka drinkers
Now your turn
Using Venn diagrams in your notebooks, decide whether each of the following arguments is valid or invalid.
Valid or invalid
• No Swedes have red noses
• Mr Luitjens has a red nose
• Therefore Mr Luitjens is not a Swede
Valid or invalid
• All IB1 boys are brave• Some brave people
are compassionate• Some IB1 boys are
compassionate
Valid or invalid
• Some physicists are frauds• Some frauds are not wealthy• Therefore some physicists are not wealthy
Valid or invalid
• All Norwegians have dogs• No good football players have dogs• Therefore no Norwegians are good football
players
Valid or invalid
• All clever girls are red-headed
• All red heads are rich• Therefore all clever
girls are rich